Magnetodielectric ceramic composite material, method of manufacturing same

Abstract

A magnetodielectric ceramic composite material comprising a first disperse phase which contains one or more magnetic ferrites, and a second, essentially continuous phase which contains electrically insulating oxides, characterized in that the electrically insulating oxides are lead(II) oxide, bismuth(III) oxide and, optionally, boron(III) oxide, is distinguished by an improved construction of the surface boundary layer. Said composite material can very suitably be used for the manufacture of frequency-selective components and wideband transmitters having a high initial permeability and a high critical frequency f 0 in the range from 1 . . . 200 MHz, and for the manufacture of monolithic, multifunctional components. A description is given of a simple method of manufacturing said composite material.

We claim: 
     
       1. A mangetodielectric ceramic composite material comprising a first disperse phase which comprises one or more magnetic ferrites, and a second, essentially continuous, phase which contains electrically insulating oxides characterized in that the electrically insulating oxides are lead (II) oxide, bismuth (III) oxide and boron (III) oxide in the molar ratios: 30<mol % PbO<80   0<mol % Bi 2  O 3  <40   0≦mol % B 2  O 3  <30.   
     
     
       2. A magnetodielectric ceramic composite material as claimed in claim 1, characterized in that the electrically insulating oxides are formed by the eutectic mixture of lead(II) oxide and bismuth(III) oxide. 
     
     
       3. A magnetodielectric ceramic composite material as claimed in claim 1, characterized in that the electrically insulating oxides are formed by the eutectic mixture of lead(II) oxide, bismuth(III) oxide and boron(III) oxide. 
     
     
       4. A magnetodielectric ceramic composite material as claimed in claim 1, characterized in that the ferrite or ferrites is or are cubic ferrite(s) having a spinel structure. 
     
     
       5. A magnetodielectric ceramic composite material as claimed in claim 1, characterized in that the ferrite or ferrites is or are manganese-zinc-ferrite(s) having a spinel structure. 
     
     
       6. A magnetodielectric ceramic composite material as claimed in claim 1, characterized in that the first disperse phase comprises monodisperse crystallites having a grain size in the range from 1 to 50 μm. 
     
     
       7. A magnetodielectric ceramic composite material as claimed in claim 1, characterized in that the first disperse phase comprises monodisperse crystallites having a grain size in the range from 5 to 15 μm. 
     
     
       8. A magnetodielectric ceramic composite material as claimed in claim 1, characterized in that it comprises electrically insulating oxides in a quantity of 0.5 to 10% by weight. 
     
     
       9. A magnetodielectric ceramic composite material as claimed in claim 1, characterized in that it comprises the electrically insulating oxides in a quantity of 1 to 3% by weight. 
     
     
       10. A sinter-impregnation process for the manufacture of a magnetodielectric ceramic composite material as claimed in claim 1, in which a porous sintered ceramic moulded body comprising one or more magnetic ferrites is impregnated with a molten phase containing PbO, Bi 2  O 3  and, optionally, B 2  O 3 . 
     
     
       11. A method of manufacturing a magnetodielectric ceramic composite material as claimed in claim 10, characterized in that the impregnating process is followed by a tempering operation for 1 to 30 hours at 600° to 900° C. 
     
     
       12. A monolithic multifunctional electronic component comprising a magnetodielectric ceramic composite material as claimed in claim 1.